Android动画实现（一）

• 自定义View实现动画

• 原理：使用View的postDelayed方法实现延迟重绘操作。在重绘操作中每次绘制不同的图形就能实现动画。

• 代码如下：

public class CircleAnim extends View {
    private Paint mPaint;
    private static final int sColor = 0x33668843;
    private int mRadius;
    private int mMaxRadius;
    private int mY;
    public CircleAnim(Context context) {
        super(context);
        initView();
    }

    public CircleAnim(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        initView();
    }

    public CircleAnim(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        initView();
    }

    public void initView(){
        Log.e("zxx", "initView");
        mPaint = new Paint();
        mPaint.setColor(sColor);
        WindowManager wm = (WindowManager) getContext().getSystemService(Context.WINDOW_SERVICE);
        mMaxRadius = wm.getDefaultDisplay().getWidth();
        mY = wm.getDefaultDisplay().getHeight();
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        Log.e("zxx","onDraw");
        //绘制不同大小圆形
        canvas.drawCircle(mMaxRadius, mY / 2, mRadius, mPaint);
        if (mRadius < mMaxRadius * 1.3){
            mRadius = mRadius + 100;
            postDelayed(new Runnable() {
                @Override
                public void run() {
                     //重绘
                    invalidate();
                }
            }, 100);
        }else{
            mRadius = 0;
            postDelayed(new Runnable() {
                @Override
                public void run() {
                    invalidate();
            },100);
        }
    }
}

• 动画效果如下